U.S. Frost Dates by Weather Station

NOAA station USC00137613 · Iowa

Frost Dates for Shenandoah, IA

NOAA weather station Shenandoah (USC00137613), Iowa · elevation 999 ft (305 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 3only 1 spring in 10 still has a frost later
  • Typical last frostApril 2050% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season179 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Shenandoah, IASpring: a frost after April 5 in 9 years out of 10, after April 20 in half of the years, after May 3 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 17 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 179 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 20First frost ~Oct 17Frost season at Shenandoah, IASpring: a frost after April 5 in 9 years out of 10, after April 20 in half of the years, after May 3 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 17 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 179 days.JFMAMJJASONDLast frost ~Apr 20First frost ~Oct 17
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 3October 1
50% (typical)April 20October 17
90% (likely)April 5October 29
Frost-free season (32°F, 50% chance)
179 days
Hard frost (28°F), last in spring, 50% chance after
April 9
Hard frost (28°F), first in fall, 50% chance before
October 26

The last 15 years (2006–2020 normals)

Typical last frost April 20 (same as the 30-year normal), typical first fall frost October 18 (1 day later). Frost-free season 181 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at Shenandoah: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 3, 20% April 29, 30% April 26, 40% April 23, 50% April 20, 60% April 17, 70% April 14, 80% April 10, 90% April 5. Observed last spring frost in recent years: 2021 April 22, 2022 April 26, 2023 May 3, 2024 April 21, 2025 April 8, 2026 May 2.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 3Apr 20Apr 52021: April 222022: April 262023: May 32024: April 212025: April 82026: May 2Fall at Shenandoah: chance of a frost before this dateFall, chance of a frost before the date: 10% October 1, 20% October 7, 30% October 11, 40% October 15, 50% October 17, 60% October 19, 70% October 22, 80% October 25, 90% October 29. Observed first fall frost in recent years: 2021 October 22, 2022 October 8, 2023 October 17, 2024 October 16, 2025 October 31.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 1Oct 17Oct 292021: October 222022: October 82023: October 172024: October 162025: October 31
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021April 22October 22
2022April 26October 8
2023May 3October 17
2024April 21October 16
2025April 8October 31
2026May 2season not over yet

What these dates mean

The cautious spring date for Shenandoah is May 3, when there is only a 10 % chance of a light frost later. Gardeners can use this date to set out tender crops with minimal risk of frost damage.

The 50% date is April 20, meaning a 50 % chance of a light frost later than this point, and the 50% date is October 17, meaning a 50 % chance of a light frost earlier than this point. The cautious fall date is October 1, when there is only a 10 % chance that a light frost has arrived earlier, allowing the final harvest of tender crops.

Hard frost, defined at 28 °F, matters more than a light frost because temperatures that low can kill plants that would otherwise survive a 32 °F event; the 50% hard-frost dates are April 9 and October 26.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after May 3" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before October 1" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Shenandoah, IANumbered nearest stations: 1 — Sidney, IA — 15 mi; 2 — Red Oak, IA — 17 mi; 3 — Clarinda, IA — 18 mi; 4 — Nebraska City, NE — 28 mi; 5 — Bedford, IA — 34 mi.IANEMO25 mi · 40 km1. Sidney, IA — 15 mi12. Red Oak, IA — 17 mi23. Clarinda, IA — 18 mi34. Nebraska City, NE — 28 mi45. Bedford, IA — 34 mi5
  1. Sidney, IA 15 mi (24 km)
  2. Red Oak, IA 17 mi (28 km)
  3. Clarinda, IA 18 mi (29 km)
  4. Nebraska City, NE 28 mi (45 km)
  5. Bedford, IA 34 mi (54 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 40.7719, -95.3567.